U.S. Pat. No. 5,834,535 describes a family of compositions in accordance with its title, "Moldable Intumescent Polyethylene and Chlorinated Polyethylene Compositions." These compositions are readily moldable by a variety of polymer molding practices into articles that have good physical strength. Moreover, the molded bodies have an additional property of serving as a heat and fire barrier. Upon exposure to a flame, they initially burn but do not melt and drip. Instead, they form a relatively strong foamed barrier of carbonized char and inorganic ceramic-like material. In some embodiments of these high density polyethylene (HDPE) and chlorinated polyethylene (CPE) compositions, a silicone elastomer (specifically, an organosiloxane) is used in addition to, or as a replacement for, some of the CPE. In many formulations the siloxane polymer improved the processibility of the material by reducing the mixing torque requirement. Further, in the molded product the polysiloxane reduced smoke evolution.
It is an object of this invention to provide a family of polyethylene and chlorinated polyethylene-based intumescent flame retardant materials containing silphenylene-siloxane elastomers for improved intumescence properties and improved processing properties.